Smarter Glass, Better Living - Blog #3

Why does double glazing make such a big difference?

Many New Zealand homes still rely on single glazed windows, which typically means:

• Significant heat loss during winter

• Prone to overheating during summer

• Condensation and “crying windows”

• And higher power bills year round

Windows are one of the biggest sources of heat transfer in New Zealand homes. In fact, windows can account for 30 - 50% of total heat loss. Even if your ceiling and walls are insulated, single glazing remains a major weak point.

What does double glazing actually do?

Retrofit double glazing replaces your existing single pane with a sealed, insulated double glazed unit, while keeping your current aluminium or timber frames. A typical double glazed unit consists of, two panes of glass, a sealed air or argon gas layer and a warm edge spacer for improved insulation. More commonly now in New Zealand homeowners are choosing the option with Low E coatings for enhanced thermal or solar performance.

By using Low E with your double glazing helps slows heat transfer reducing heat loss in winter and unwanted heat gain in summer, creating a far more stable and comfortable indoor environment in your home.

A double glazed unit significantly slows heat transfer, reducing heat loss in winter and unwanted heat gain in summer creating a much more stable indoor environment for your home.

Do I need consent for retrofit double glazing in New Zealand?

In most cases for retrofit double glazing where the existing aluminium or timber frames remain in place (a like for like glazing upgrade), building consent is often not required. However, requirements can vary depending on frame condition, weathertightness, and project details, so if you’re unsure ask our team.

For most homeowners this approach keeps your retrofit double glazing project simple offering a straightforward way to improve insulation, warmth, and comfort without the delays and costs associated with a full replacement window/ new joinery.

Here are the real world benefits and the impact of Double Glazing in New Zealand

1.      A warmer home in winter

Many kiwi homes struggle to stay warm, particularly those built before double glazing became mandatory in 2007 for new builds. While older homes are exempt retrofit double glazing is a great way to bridge the gap and dramatically improve comfort.

Double glazing helps by:

• Keeping the inside glass surface warmer

• Reducing cold drafts

• Improving overall thermal performance

Using Metro’s Low E glass, homes can retain up to 79% more heat compared to single glazing, that’s a noticeable difference on cold mornings. To find out more Click here to view Metro’s full Low E range.

2.     A cooler home in summer

With stronger sun and rising summer temperatures, overheating is now a common issue especially in north, east, and west facing rooms.

With the right solar control Low E glass, double glazing can:

• Reduce harsh solar gain

• Keeps rooms brighter without dark tints

• Improves comfort on hot days

With the right solar control using Metro’s Low E glass can reduce up to 74% of the sun’s heat compared to single glazing. Choosing glass based on orientation and climate zone is key there’s no one size fits all solution. To find out more Click here to view Metro’s Low E range.

 3.     Reduce the likelihood of condensation or crying windows

Condensation is one of the most searched home issues in New Zealand. By keeping the internal pane warmer, double glazing can significantly reduce the conditions that cause moisture to form.

Homeowners experience:

• Less morning moisture

• Lower risk of mould and mildew

• Drier, healthier living space

• Better protection for curtains and timber frames

While double glazing makes a big difference it is not the sole answer, it works best alongside good ventilation, as everyday activities like cooking, laundry and showers still introduce moisture into the home.

4.     Lower power bills and more energy efficient

Because windows contribute so heavily to heat loss, upgrading them has a direct impact on power use.

With retrofit double glazing, many homeowners notice:

• Less reliance on heaters and heat pumps during winter and summer

• More consistent indoor temperatures year round

• Heating systems working more efficiently

• Lower long term power costs

For older homes, double glazing helps bridge the gap toward healthier, more comfortable living standards.

5.     Reduce noise - quieter and peaceful homes

Double glazing also helps reduce noise transfer. The insulated gap between the two panes especially when paired with acoustic laminated glass can reduce outside noise/ sound transmission through your glass.

This is particularly effective for bedrooms, nurseries, home offices or street facing living areas.

6.     Lower UV and fading damage

New Zealand has some of the highest UV levels in the world. The right glass combination which includes solar control Low E and laminate options can significantly reduce UV entering your home, helping protect your furniture, floors, carpets and curtains. It can also protect artwork and interiors over time.

Customise glass choices for every room

The real impact of double glazing comes from choosing the right glass for the right room.

For example:

• Living areas on the sunny side of your home may need solar control Low E

• Bedrooms benefit from high insulation Low E

• Street facing rooms may need acoustic or privacy glass

Every window can be tailored to suit your home’s layout, climate zone, and lifestyle  something we carefully consider during every in home consultation.

Is retrofit double glazing worth it?

For most New Zealand homes, the answer is yes. Retrofit double glazing offers:

• A warmer home in winter

• Lower power bills year round

• Less likelihood of condensation forming

• Improved comfort and quieter living

• And higher property value

All without replacing your existing frames, disturbing cladding, or undertaking a full renovation. It’s one of the more cost effective window upgrades available in New Zealand. 

FAQs

What is the impact of double glazing?

Double glazing improves insulation and can reduce heat loss by up to 50%. It helps minimise condensation, reduce noise, lower power bills, and improve year round comfort.

What does double glazing do in a New Zealand home?

Double glazing helps reduce heat transfer through windows, making homes easier to keep warm, drier, and quieter compared with single glazing.

Does double glazing work with existing frames?

Yes, retrofit double glazing replaces the single glass, not the frames, and works with both aluminium and timber joinery.

Does double glazing stop condensation completely?

No. Double glazing reduces the likelihood of window condensation, but moisture levels are also influenced by ventilation, heating, and what is happening inside your home

Is retrofit double glazing suitable for older NZ homes?

Yes. Retrofit double glazing is commonly installed into existing timber or aluminium frames, making them suitable for many older New Zealand houses.

Will double glazing keep my home warmer?

Absolutely. Double glazing especially paired with the right Low E can reduce heat loss dramatically, helping maintain a warmer, drier and comfier temperature year round

Does double glazing make a home warmer in winter and cooler in summer?

Low E technology helps slows heat transfers in both directions, helping retain indoor warmth in winter and limiting heat gain during summer.

How is retrofit double glazing different from full window replacement?

Retrofit double glazing keeps the existing window frame and replaces the glass unit, whereas full replacement involves removing and installing new window frames.